1. Field of the Invention
The present invention related to a GaN transistor, particularly an enhanced GaN transistor with the P-N junction.
2. Description of the Prior Art
Because the gallium nitride high electron mobility transistor (GaN-HEMT) possesses higher output power, higher breakdown voltage and high-temperature resistance etc., the GaN-HEMT has been widely used in high power circuit in recent years.
As for the conventional GaN transistor, because the gallium nitride/aluminum nitride in its structure possesses a great amount of polar charge to form two dimension electron gas (2DEG), so that the transistor should be operated under the depletion mode. Under this mode, the transistor is called the normal on transistor. Because the threshold voltage of the normal on transistor is negative, the transistor will still be able to conduct the current, which may cause extra power consumption.
In the prior art, the recessed gate or carbon tetrafluoride (CF4) plasma or P-type gallium nitride gate has been proposed to make the enhanced GaN transistor. In the transistor with conventional AlGaN/GaN heterostructure, its AlGaN buffer layer has some problems, such as mismatch lattice constant, thermal expansion variance and tensile strength etc. Thus, the maximum output current will be constrained.